fix(example-todo-list): add steps to run in sql db #2448

dhmlau · 2019-02-21T21:05:27Z

There are extra steps needed in order to run the todo-list application on relational database. This PR listed the steps.

Checklist

npm test passes on your machine
New tests added or existing tests modified to cover all changes
Code conforms with the style guide
API Documentation in code was updated
Documentation in /docs/site was updated
Affected artifact templates in packages/cli were updated
Affected example projects in examples/* were updated
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raymondfeng · 2019-02-25T20:55:46Z

docs/site/todo-list-tutorial-sqldb.md

+
+The Repository classes are used to bind the datasource and the models. Since
+we've changed to another datasource, we need to update the repositories which
+are located in the `src\repositories` folder.


src/repositories?

raymondfeng · 2019-02-25T20:56:33Z

docs/site/todo-list-tutorial-sqldb.md

+For details, see the [Database migrations](Database-migrations.md) documentation
+page.
+
+### Alter tables to define the foreign keys


IIRC, postgresql connector already supports foreign key constraints? Can you verify?

I ran the npm run migrate command and it didn't create the foreign key constraints. Do I need to do something else?

Creating FK requires defining them in the model similar to MySQL. see
https://github.com/strongloop/loopback-connector-postgresql#auto-migrateauto-update-models-with-foreign-keys

let me give it a try tomorrow. Thanks @elv1s.

@raymondfeng @elv1s , I think I could use some help here. In todo.model.ts, I'm trying to add the property settings that @elv1s mentioned above:

@property({ postgresql: { foreignKeys: { fk_todo_todoListId: { name: 'fk_todo_todoListId', entity: 'TodoList', entityKey: 'id', foreignKey: 'todoListId', }, }, }, }) @belongsTo(() => TodoList) todoListId: number;

However, it complained that I cannot apply more than one decorator:
Error: Decorator cannot be applied more than once on Todo.prototype.todoListId when running npm run migrate.
@elv1s, were you able to get it running? Am I missing something? Thanks!

I think we need to remove the call to property() decorator inside belongsTo() so we can add property metadata like you've shown above @dhmlau (see #2256 (comment)).

@dhmlau The foreignKeys need to be defined in @model.

Issues #2345, #2256, and PR #2442 are related to this in that the db field value of todoListId cannot be updated when we already have a decorator associated to it. So if PK and FK are different types in the DB then creating the constraint will fail.

Also order of creation of the table is important. TodoList must exist when creating the Todo FK constraint.

Multiple decorators are not supported.

@model({ settings: { foreignKeys: { fk_todo_todoListId: { name: 'fk_todo_todoListId', entity: 'TodoList', entityKey: 'id', foreignKey: 'todoListId', }, }, }, }, })

@elv1s @raymondfeng , thanks for the info. I managed to get it working! :) Will work on the PR tomorrow.

bajtos · 2019-03-11T14:58:14Z

docs/site/todo-list-tutorial-sqldb.md

+
+```ts
+constructor(
+    @inject('datasources.psqlds') dataSource: juggler.DataSource,


IIUC, as a result of this tutorial step, we end up with two datasources in our project:

db datasource backed by memory connector - NOT USED BY ANY REPO

psqlds datasource backed by postgresql connector - USED EVERYWHERE

I don't like the idea of having a datasource that's not used by any repository.

Also I consider it as a bad practice to name artifacts after implementation details. It's better to name them after our intention & their function. The datasource called db is meant to be the primary data storage used by the application.

Can we find a way how to preserve db datasource name please?

For example, we can tell users to simply change the configuration of the existing db datasource to use postgresql instead of memory connector.

If we want a more interactive approach that will prompt them for PostgreSQL config, then perhaps we can tell them to rm src/datasources/db.datasource.* and run lb4 datasource db to re-create it with different config.

bajtos · 2019-03-11T15:15:22Z

I think this PR is pretty much blocked by #2442

b-admike · 2019-04-24T19:49:21Z

docs/site/todo-list-tutorial-sqldb.md

+Similar to the `Todo` model, we will specify the constraints in the `settings`.
+
+```ts
+@model({


The FK definitions here seem the same as above ^

will fix it as @jannyHou suggested.

jannyHou

@dhmlau Nice doc! Added a few comments.

jannyHou · 2019-04-24T20:36:46Z

docs/site/todo-list-tutorial-sqldb.md

+@model({
+  settings: {
+    foreignKeys: {
+      fk_todo_todoListId: {


wouldn't this be fk_todoListImage_todoListId?

you're right. let me fix it.

jannyHou · 2019-04-24T20:40:22Z

docs/site/todo-list-tutorial-sqldb.md

+The order of table creation is important. We are going to migrate `TodoList`
+model first and then `Todo` and `TodoListImage` models.
+
+1. We'll run the database migration on the `TodoList` table. In


I am wondering...why we don't run the migrate command only once with config models: ['TodoList', 'Todo', 'TodoListImage']?

Would the migration happen in this order? If yes, that's even better. let me give it a try. thanks.

it is working! I've fixed my docs accordingly.

jannyHou

LGTM 🚢

nabdelgadir

Looks good 👍, just have some nitpicks (you can ignore them).

nabdelgadir · 2019-04-25T12:54:15Z

docs/site/sidebars/lb4_sidebar.yml

@@ -70,6 +70,10 @@ children:
      url: todo-list-tutorial-controller.html
      output: 'web, pdf'

+    - title: 'Running on relational database'


Suggestion: on relational -> on a relational (same for the title and summary).

maybe running on relational databases?

sounds good!

nabdelgadir · 2019-04-25T12:57:00Z

docs/site/todo-list-tutorial-sqldb.md

+
+If you are running this example using a relational database, there are extra
+steps in order to set up constraints in the database. We're using PostgreSQL for
+illustration, it would work for other relational databases in a similar way.


Nitpick: it would... -> but it would...

nabdelgadir · 2019-04-25T13:00:09Z

docs/site/todo-list-tutorial-sqldb.md

+![database tables](todo-list-tutorial-dbtables.png)
+
+{% include note.html content="
+There is an ongoing work on supporting strong relation with referential integrity.  For details, please see [epic #2231](https://github.com/strongloop/loopback-next/issues/2331).


Nitpick: There is an ongoing work -> There is ongoing work, relation -> relations

nabdelgadir · 2019-04-25T13:00:53Z

docs/site/todo-list-tutorial-sqldb.md

+We will use the `foreignKeys` attribute to determine the constraints in the
+database table.
+
+In `src\models\todo.model.ts`, add the `settings` options in the `@model`


src/models/todo.model.ts?

oops. yes. thanks.

nabdelgadir · 2019-04-25T13:03:55Z

docs/site/todo-list-tutorial-sqldb.md

+The order of table creation is important. We are going to migrate `TodoList`
+model before the `Todo` and `TodoListImage` models.
+
+In `src\migrate.ts`, modify this line:


src/migrate.ts?

elv1s

LGTM

dhmlau · 2019-04-30T23:42:44Z

@bajtos @raymondfeng, may I get your reviews again and see if I addressed your comments? Thanks.

bajtos

Looks mostly good, I have few minor comments to consider.

No further review is necessary from my side.

docs/site/todo-list-tutorial-sqldb.md

bajtos · 2019-05-03T12:43:38Z

docs/site/todo-list-tutorial-sqldb.md

+  },
+})
+export class Todo extends Entity {
+```


Let's add little bit more code to make the snippet self-contained. At the moment, it's breaking syntax highlighting here on GitHub.

export class Todo extends Entity { // etc. }

bajtos · 2019-05-03T12:44:05Z

docs/site/todo-list-tutorial-sqldb.md

+    },
+  },
+})
+export class TodoListImage extends Entity {


Ditto.

export class TodoListImage extends Entity { // etc. }

docs/site/todo-list-tutorial-sqldb.md

bajtos · 2019-05-03T12:45:36Z

docs/site/todo-list-tutorial-sqldb.md

+```ts
+await app.migrateSchema({
+  existingSchema: existingSchema,
+  models: ['TodoList', 'Todo', 'TodoListImage'],


Are you sure this line is necessary? I believe that app.migrateSchema is going to migrate ALL models by default. By omitting the list of models, we keep the code forward-compatible. In your proposal, developers adding new models in the future must remember to update the migration script too.

From my experiment, this line is necessary. TodoList table must be created first before Todo and TodoListImage. When I didn't specify the order, I will get an error about the TodoList table do not exist. I'm not sure what's the better way to specify the order but this change seems to be working for me.

Discussed with @bajtos. He suggested:

Add comments in the above code snippet to explain why we need to do this. -- DONE

Open a GH issue to investigate how we can improve the migration tool so that users don't need to explicitly specify the order. -- [Spike] Automigrate: no need to specify the order of tables to be migrated #2831 is created.

dhmlau requested review from bajtos and raymondfeng as code owners February 21, 2019 21:05

dhmlau requested a review from b-admike February 21, 2019 21:05

raymondfeng reviewed Feb 25, 2019

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bajtos added Examples feature Docs labels Mar 5, 2019

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dhmlau mentioned this pull request Apr 1, 2019

Relations not working in loopback 4 using mysql database How to solve it loopbackio/loopback-connector-mssql#202

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dhmlau force-pushed the example-docs branch 2 times, most recently from 8bddb2e to e2d4a9b Compare April 24, 2019 19:15

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dhmlau force-pushed the example-docs branch from b3cb679 to 0cf147e Compare April 24, 2019 21:46

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fix(example-todo-list): add steps to run in sql db

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dhmlau mentioned this pull request May 3, 2019

[Spike] Automigrate: no need to specify the order of tables to be migrated #2831

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dhmlau merged commit 0122211 into master May 3, 2019

dhmlau deleted the example-docs branch May 3, 2019 15:00

fix(example-todo-list): add steps to run in sql db #2448

fix(example-todo-list): add steps to run in sql db #2448

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dhmlau commented Feb 21, 2019

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elv1s Mar 8, 2019 •

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